Front View	Rear View	Side View

Technical Details

I acquired my Offset Ascending Rack (OAR) from the inventor, Gordon Svedberg in 2010.

My Offset Ascending Rack is 142 mm. tall, 119 mm. wide, 45 mm. thick, and weighs 416 g. The OAR consists of a central spine and three rather complex arm assemblies, as follows:

• The spine is made from a 142 mm. length of 1" × 1/2" (25.4 × 12.7 mm.) aluminum alloy, probably 6061-T6 series. There are two 16 mm. holes drilled in the spine.
• The top arm assembly is connected to the spine with a 1 3/8" 1/4-20 UNC stainless steel bolt and lock nut. It consists of the following:
  • On the front: A 127 mm. long, 1" × 1/4" (25.4 × 6.4 mm.) 6061-T6511 aluminum alloy arm supporting two 21 mm. long, 5.9 mm. diameter stainless steel pins, the inner one surrounded by an 8.4 mm. tube apparently made from a roll pin. A sprocket chain link connector pop-riveted to the arm supports the pins. There is a brass washer between the bolt head and the arm, and a stainless steel fender washer between the arm and the spine.
  • On the rear: There is a larger sprocket chain link connector that pivots on the bolt, and a smaller one that connects the bolt and the inner pin on the arm. The outer end of the larger connector has a smaller connector attached to it by a round countersunk Phillips-head machine screw and lock nut. A spring between the small connector and nut allows the small connector to move with respect to the larger one. This allows rigging the rope between the two pins on the arm, and then moving the connector between the pins to secure the rope in place.
• The middle arm assembly is connected to the spine with a 1 3/8" 1/4-20 UNC stainless steel bolt and lock nut. It consists of the following:
  • On the front: There is a small sprocket chain link connector that connects the bolt and the inner pin on the arm. Three steel and one brass washers serve as spacers between the link and the pin.
  • On the rear: A 97 mm. long, 1" × 1/4" (25.4 × 6.4 mm.) 6061-T6511 aluminum alloy arm supporting two 21 mm. long, 5.9 mm. diameter stainless steel pins, the inner one surrounded by an 8.4 mm. tube apparently made from a roll pin. A sprocket chain link connector pop-riveted to the arm supports the pins. There is a brass washer between the bolt head and the arm, and a small steel washer between the arm and the spine.
• The lower arm assembly is connected to the spine with a 1 3/8" 1/4-20 UNC stainless steel bolt and lock nut. It consists of the following:
  • On the front: A 63 mm. long, 1" × 1/4" (25.4 × 6.4 mm.) 6061-T6511 aluminum alloy arm supporting two 21 mm. long, 5.9 mm. diameter stainless steel pins, the inner one surrounded by an 8.4 mm. tube apparently made from a roll pin. A sprocket chain link connector pop-riveted to the arm supports the pins. There is a brass washer between the bolt head and the arm, and a stainless steel fender washer between the arm and the spine.
  • On the rear: There is a larger sprocket chain link connector that pivots on the bolt, and a smaller one that connects the bolt and the inner pin on the arm.

The spine is stamped "OAR" and "009" (the serial number). Stock material markings on the top arm show that it is made from 6061-T6511 aluminum alloy.

Comments

The OAR is designed for arborists. They can use it to ascend or descend. Rather than describe the motion, I'll refer the reader to two of the inventors YouTube videos. One shows how to use the OAR, and another shows an OAR drop test.

The OAR workmanship suggests that it was done in a home shop, primarily with hand tools; however, the inventor is marketing these.